Structural and conductivity investigations of doped Li-titanates (original) (raw)
ASEAN Journal on Science and Technology for Development, 2017
Bulk nanostructured perovskites of La0.67-xLi3xTiO3 (LLTO) were prepared by using thermally ball-grinding from compounds of La2O3, Li2CO3 and TiO2. From XRD analysis, it was found that LTTO materials were crystallized with nano-size grains of an average size of 30 nm. The bulk ionic conductivity was found strongly dependent on the Li+ composition, the samples with x = 0.11 (corresponding to a La0.56Li0.33TiO3 compound) have the best ionic conductivity, which is ca. 3.2 x 10-3 S/cm at room temperature. The LLTO amorphous films were made by electron beam deposition. At room temperature the smooth films have ionic conductivity of 3.5 x 10-5 S/cm and transmittance of 80%. The optical bandgap of the films was found to be of 2.3 eV. The results have shown that the perovskite La0.56Li0.33TiO3 thin films can be used for a transparent solid electrolyte in ionic battery and in all-solid-state electrochromic devices, in particular.
2015
exhibited high lithium insertion. Table 3.11 depicts specific capacitance for the copper coated electrodes used for the battery type supercapacitors. As a result of this performance, these compounds could also be seen as promising materials for supercapacitors. The active mass used was only 0.2 g per electrode sheet at laboratory scale, in comparison to the commercial films where (5-8) g is used. Li x Fe y Ti 3-x-y O 3 (1 ≤ x ≤ 1.75 and 0.75 ≤ y ≤ 1.5) as a second series has been investigated as a possible positive electrode for use in lithium ion batteries. These compositions are rock salt members of the solid solution between LiFeTiO 4 and Li 4 Ti 5 O 12 composition. X-ray patterns confirmed the presence of a disordered rock salt phase instead of a mixture of spinel and rock salt as earlier reported. Rock salt composition x = 1.75, y = 0.75 showed a capacity of 207 mA h g-1 over 25 cycles in comparison to spinels, LiMn 2 O 4 and LiNiO 2 (148 and 140) mA h g-1 , respectively. Third investigated composition was carbon doped ramsdellite lithium titanate, LiTi 2 O 3.75 C 0.25. This phase was produced in a two-step method, firstly, carbon was doped using the precursor Ti 2 OC, to form LiTi 2 O 3.75 C 0.25 , and later Li was extracted using an acid oxidation method. Both XRD analysis and TGA revealed the phase formation and purity. The phase pure Ti 2 O 3.75 C 0.25 powder was tested in a Li cell configuration in combination with Li metal anode and LiClO 4 as the electrolyte. The electrochemical properties were determined via redox cycling in (0-3.0), (0.5-2.8) and (1.2-1.3) V potential windows, revealing various sites for Li ion intercalation. The
International Journal of Integrated Engineering
Lithium-ion battery has been drawing attention from researchers due to its excellent properties in terms of electrochemical and structural stability, low cost, and high safety feature, leading to prospective applications in electric vehicles and other large-scale applications. However, lithium-ion batteries are still in charging time owing to its low conductivity, restricting its wide applications in large-scale applications. In this work, therefore, lithium lanthanum titanate (LLTO) was synthesized derived from lanthanum oxalate, as a lanthanum source, for an anode active material application in the lithium-ion batteries due its high electrochemical conductivity and pseudocapacitive characteristics. To the best our knowledge, our work is the first one to synthesize LLTO from lanthanum oxalate as the lanthanum source. Commercial lithium carbonate and commercial titanium oxide were used as the lithium and titanium sources, respectively. It was used low cost and simple solid-state rea...
Ionics, 1996
The lithium ionic conducting perovskite Lao.57Lio.3TiO 3 has been synthesised via a solgel method at a temperature of 700 ~ The crystallinity of the product can be greatly increased by further heat treatment at 1000 ~ In this paper the product of the sol-gel synthesis is compared with the product of conventional solid-state synthesis, and the influence of the synthesis method as well as of quenching on the crystal structure and ionic conductivity has been studied. ACimpedance measurements show two contributions to the ionic conductivity, which can be adscribed to intergranular and intragranular effects, respectively. A lower intergranular resistivity is observed for sol-gel samples, while quenching mainly affects the materials prepared by solid-state reaction. The crystal structure of the material prepared by the sol-gel method is identical to that of the material prepared by the solid state reaction, although the synthesis temperature is nearly 600 ~ lower. A tetragonal superstructure is observed when either type of material is slowly cooled from 1300 ~ Quenching from the same temperature results in the suppression of that superstructure.
Crystalline Perovskite La 0.67-xLi 3x TiO 3: Preparation and Ionic Conducting Characterization
Communications in Physics, 2007
Crystalline perovskite La0.67-xLi 3x TiO 3 with x = 0.06, 0.11 and 0.15 were prepared by solid-state-solution reactions at 1350 0 C from TiO 2 , La 2 O 3 and Li 2 CO 3 Crystalline structure of these compounds was analyzed by XRD method. The ionic conducting property of La 0.67-x Li 3xTiO 3 was characterized on AutoLab. Potentiostat-PGS30 system with impedance technique using fitting software program available in the equipment. The highest ion conductivity at room temperature was found for the compound with x =0.11, namely sigma\sigmasigma = 3.1 x 10 -5Scm -1. With increase of temperature the ionic conductivity increased and at 2000C it reached a value in two orders in magnitude higher (6 x 10 -3Scm -1). The activation energy of the compounds was determined on Ln($\sigma$) vs. 1/T plots and found to be as low as 0.36 eV.
Solid State Ionics, 2015
With the aim to improve the ionic conductivity of perovskite materials used for all-solid-state batteries, La (2/3) − x Li 3x TiO 3 with x = 0.11 (LLTO11) ceramics was prepared by a double mechanical alloying method. The influence of thermal treatments (furnace-cooling, SC and quenching, QC) on the crystalline structure and Li-ion conductive properties of the LLTO ceramics has been studied by X-ray powder diffraction (XRD), Raman scattering and impedance spectroscopy. XRD patterns of SC-samples exhibited a doubled perovskite with a tetragonal structure, whereas those of quenched samples indicated a simple cubic perovskite. The increase in the ionic conductivity of the LLTO11 ceramics was attributed to the disordered morphology that has promoted 3D-conductive mechanism. At room temperature, the grain and grain-boundary conductivities of the quenched LLTO11 ceramics reached values as large as 1.8 × 10 −3 S•cm −1 and 7.2 × 10 −5 S•cm −1 , respectively. All-solidstate batteries made from the LLTO11 solid-state electrolyte combining with LiMn 2 O 4 , and SnO 2 thin films as cathode and anode, respectively, possessed a charge-discharge efficiency of~61% and a charging capacity of 3.0 μAh/(cm 2 • μm) at a voltage of 1.6 V.
Communications in Physics, 2009
Perovskite La0.67-xLi3xTiO3 with x = 0.10, 0.11, 0.12 and 0.13 were firstly annealed at 800 oC then treated by reactive milling, followed by post-annealing at temperatures from 1100 to 1200oC. The crystalline structure of grain and grain-boundary were characterized by XRD and SEM. The impedance measurements showed that nanocrystalline La0.67-xLi3xTiO3 after being annealed at 1150 oC possessed a grain conductivity as high as 1.3×10-3 S.cm-1. The grain-boundary conductivity was enhanced one order in magnitude after annealing at temperature higher 1100oC and consists of 5.8×10-5 S.cm-1. The results have also showed the limitation of the adiabatic thermal treatment for the improvement of the grain-boundary conductivity and suggested the way to overcome the limitation by rapidly cooling the samples from the high temperature to room temperature.
Solid electrolytes based on lithium-containing lanthanum metaniobates
Journal of the European Ceramic Society, 2004
The structure and transport properties of lithium-containing lanthanum metaniobates with defect-perovskite structure, La 2/3-x Li 3x & 4/3-2x Nb 2 O 6 , have been studied. It has been shown that in the structure of La 2/3-x Li 3x & 4/3-2x Nb 2 O 6 , Li + cations occupy, preferably, positions 1a in the range x=0À%0.5, and occupy positions 1c (vacancies) at x> 0.5. It has been noted that the direction 1c$1c is energetically a more favorable pathway of lithium ion migration. It has been shown that the materials under investigation possess a high lithium ion-conductivity. #
Lithium-7 NMR and ionic conductivity studies of lanthanum lithium titanate electrolytes
Solid State Ionics, 1997
Gel electrolytes synthesized from poly(methylmethacrylate), ethylene carbonate, propylene carbonate and various lithium salts [LiClO,, LiAsF,, or LiN(CF,SO,),] have been investigated by differential scanning calorimetry, electrical conductivity, and Ll, ' 19F and 75As NMR spectroscopy. Although the ionic conductivities of the gels approach those of liquid electrolytes above room temperature, the NMR results indicate that the immediate environments of both the cations and anions differ significantly in the gel and in the liquid. Thus the presence of microscopic regions of pure liquid electrolyte in the gel can be ruled out.